Working with Fractions

Nina Kennedy

Content Area: Mathematics

Grade Level: 4th

Summary: The purpose of this instructional PowerPoint is to help students understand the basic functions of fractions.

Learning Objective: At the end of this lesson, given equations to evaluate, the student will be able to add and subtract fractions with both alike and different denominators with 100% accuracy.

Content Standard: Understand adding and subtracting of fractions.

Accomplishment: Identify and analyze the numerator and denominator of fractions.

Understanding Fractions

A simple fraction is made up of two numbers: The top number is called the NUMERATOR and the bottom number is called the DENOMINATOR.

34

In this fraction the number 3 is the numerator and the number 4 is the denominator.

The DENOMINATOR represents how many equal pieces something has beendivided into. In the fraction above, the 4 means that there are 4 equal pieces thatmake up a whole.

The NUMERATOR represents how many of those pieces are still present. In the fraction above, the 3 means that there are 3 out of a total 4.

A fraction means division.

34 Means 3 4

Any whole number represented as a fraction is simply written over the number 1. For example.

3= -4 1

31

-4=

Which of the following fractions represents how many pieces are left?

The correct answer would be 5/9 because there are 5 pieces remaining out of 9 total.*The fraction 4/9 represents how many of the pieces are missing from the total 9.

Adding and Subtracting Fractions with the same Denominators

It is easy to add fractions as long as they have the exact same denominator. You just simply add the numerators together and leave the denominator the same. For example:

24

14+ = 2+1

4= 3

4The same steps are taken when you subtract fractions. As long as the denominators are the same you just subtract the numerators. For example:

79

29- = =7-2

959

Adding and Subtracting Fractions with different Denominators

• When two fractions have different denominators, we must rewrite them with a common denominator in order to add or subtract them.

6 is a common multiple of 2 and 3.

Change fraction #1 to an equivalent fraction with a

denominator of 6, then multiply top and bottom number by 3

Change fraction #2 to an equivalent fraction with the

same denominator of 6 – multiply top and bottom by 2.

12

13

12

36

13

26

+

x 3x 3 =

x 2x 2 =

Now that both fractions have the exact same denominator, we are ready to add

them together.

36

26 + = 5

6When subtracting fractions with different denominators you would use the sameprocess to make both of them the same. Once you have done so you can subtract the Numerators and keep the denominator. For instance:

23

56 - = 4

656 = =

=2+3 6

5-4 6

16

New fractions with common

denominator

Now that we understand simple fraction and how to add or subtract them, lets

practice.

Directions: Use what you have learned in this lesson to solve the following problems. You may work with another student to compare answers. You have 3 minutes.

1. 2 + 1 3 6

2. 3 - 1 4 2

3. 5 + 2 8 8

Now, let’s check our work! Your answers should look similar to this:

1. 5/6

2. 1/4

3. 7/8

STOP

This concludes the lesson on working with fractions. Each student should be able to

understand the concept of adding and subtracting fractions with both alike and

different denominators. Each student should also be able to recognize a simple fraction and

understand the difference between the numerator and the denominator.